pitch in
1．start work eagerly 努力投入工作
If everyone pitched in we'll soon have the job finished．如果每个人都拼命干，我们很快就能把活干完。
2．give help or money for sth．；contribute帮助某事；捐献
He wouldn't have finished the painting if his wife hadn't pitched in．如果没有他妻子尽力协助，这幅画他就完不成了。
We all pitched in 5 yuan to buy her a present．我们每人都捐5块钱买了一份礼物送给她。